What is the BBCOR Certification?

Bat Resource Guide

BBCOR (Bat-Ball Coefficient of Restitution) is something you've
probably heard a lot about recently; it's the new standard currently
governing adult baseball bats used in collegiate play, and it will be
implemented for high school play in 2012. Rather than measuring the
ratio of the ball exit speed to pitch and bat speeds (like with BESR),
BBCOR measures the trampoline effect of the bat. In the past, when a
pitched ball made contact with an alloy or composite bat, the barrel
would flex inward ever so slightly and the ball would retain some of its
energy resulting in farther hits. Wood bats don't have as much "give"
to them and the ball loses much of its energy upon impact. The BBCOR
standard ensures that non-wood bats perform more comparably to wood bats
in an attempt to level the playing field.

What Happened to BESR?

Ball Exit Speed Ratio (BESR) is the standard that formerly governed
adult baseball bats. BESR is found by finding the ratio of ball exit
speed to the combined speeds of pitched ball and swung bat.